A novel cellulose-based macromolecular chain transfer agent (Cell-CTA) was designed to prepare cellulose graft copolymers via reversible addition-fragmentation chain transfer (RAFT) polymerization. A series of cellulose-graft-poly(n-butylacrylate-co-acrylamide) (Cell-g-P(BA-co-AM)) copolymers were synthesized as thermoplastic elastomers (TPEs). In this molecular structure, cellulose chains were used as semirigid backbones, whereas the P (BA-co-AM) side chains acted as the rubbery matrix. The glass transition temperatures (T(g)s) of Cell-g-P(BA-coAM) copolymers can be manipulated by tuning the molar ratios between BA and AM during the polymerization process. These cellulose graft copolymers show typical elastomeric behavior and can possess strong tensile strength and high toughness according to the mechanical tests. The random distributed amide groups in AM units can form strong self-complementary hydrogen bonding as supramolecular cross-linking points in the graft copolymers. Morphological results demonstrate the homogeneous state of these Cell-g-P(BA-co-AM) copolymers. This convenient and robust grafting strategy can be further utilized to generate various cellulose-based graft copolymers as sustainable materials via rational molecular design.